# plcont.3plplot - Man Page

Contour plot

## Synopsis

**plcont**(*f*, *nx*, *ny*, *kx*, *lx*, *ky*, *ly*, *clevel*, *nlevel*, *pltr*, *pltr_data*)

## Description

Draws a contour plot of the data in *f*[*nx*][*ny*], using the *nlevel* contour levels specified by *clevel*. Only the region of the matrix from *kx* to *lx* and from *ky* to *ly* is plotted out where all these index ranges are interpreted as one-based for historical reasons. A transformation routine pointed to by *pltr* with a generic pointer *pltr_data* for additional data required by the transformation routine is used to map indices within the matrix to the world coordinates.

Redacted form: **plcont(f, kx, lx, ky, ly, clevel, pltr, pltr_data)** where (see above discussion) the pltr, pltr_data callback arguments are sometimes replaced by a tr vector with 6 elements; xg and yg vectors; or xg and yg matrices.

This function is used in examples 9, 14, 16, and 22.

## Arguments

*f*(**PLFLT_MATRIX**(3plplot), input)A matrix containing data to be contoured.

*nx, ny*(**PLINT**(3plplot), input)The dimensions of the matrix

*f*.*kx, lx*(**PLINT**(3plplot), input)Range of x indices to consider where 0 <= kx-1 < lx-1 < nx. Values of kx and lx are one-based rather than zero-based for historical backwards-compatibility reasons.

*ky, ly*(**PLINT**(3plplot), input)Range of y indices to consider where 0 <= ky-1 < ly-1 < ny. Values of ky and ly are one-based rather than zero-based for historical backwards-compatibility reasons.

*clevel*(**PLFLT_VECTOR**(3plplot), input)A vector specifying the levels at which to draw contours.

*nlevel*(**PLINT**(3plplot), input)Number of contour levels to draw.

*pltr*(**PLTRANSFORM_callback**(3plplot), input)A callback function that defines the transformation between the zero-based indices of the matrix

*f*and the world coordinates.For the C case, transformation functions are provided in the PLplot library:**pltr0**(3plplot) for the identity mapping, and**pltr1**(3plplot) and**pltr2**(3plplot) for arbitrary mappings respectively defined by vectors and matrices. In addition, C callback routines for the transformation can be supplied by the user such as the mypltr function in examples/c/x09c.c which provides a general linear transformation between index coordinates and world coordinates.For languages other than C you should consult the PLplot documentation for the details concerning how**PLTRANSFORM_callback**(3plplot) arguments are interfaced. However, in general, a particular pattern of callback-associated arguments such as a tr vector with 6 elements; xg and yg vectors; or xg and yg matrices are respectively interfaced to a linear-transformation routine similar to the above mypltr function;**pltr1**(3plplot); and**pltr2**(3plplot). Furthermore, some of our more sophisticated bindings (see, e.g., the PLplot documentation) support native language callbacks for handling index to world-coordinate transformations. Examples of these various approaches are given in examples/<language>x09*, examples/<language>x16*, examples/<language>x20*, examples/<language>x21*, and examples/<language>x22*, for all our supported languages.*pltr_data*(**PLPointer**(3plplot), input)Extra parameter to help pass information to

**pltr0**(3plplot),**pltr1**(3plplot),**pltr2**(3plplot), or whatever callback routine that is externally supplied.

## Authors

Many developers (who are credited at http://plplot.org/credits.php) have contributed to PLplot over its long history.

## See Also

PLplot documentation at http://plplot.org/documentation.php.